Hairy Earthtongue Identification Guide

The setting and the first glance

Earthtongues are found by people who are already looking down and moving slowly. The classic ground is unimproved, nutrient-poor grassland: an old churchyard, a mossy lawn that has never been fertilised, a species-rich meadow, a damp mossy bank, a flush in acid grassland, the mossy edge of a bog or dune slack. Trichoglossum hirsutum pushes up between mosses, and because it is matt black against dark green it is genuinely difficult to see until your eye adjusts. Once it does, you usually find several, because it grows in small troops scattered over a few square metres.

The first impression is of small black tongues or narrow paddles standing two to eight centimetres tall, straight or slightly curved, dull rather than glossy. In low sunlight they catch the light along their edges with a faint bloom, which is the first hint of the character that names the species.

Shape and proportions

The fruitbody is a club divided into two clearly different parts. The upper part, the fertile head, is flattened and lance-shaped to spathulate, often with a shallow groove running down each face, and it usually occupies between a quarter and a half of the total height. Below it the stalk continues as a slender, more or less cylindrical, sometimes slightly compressed stem.

Crucially, the transition between head and stalk is abrupt and clearly marked. You can see where the fertile tissue stops and the sterile stalk begins — the head is broader, flatter and sharply set off. Fruitbodies that taper gradually from top to bottom with no clear boundary belong elsewhere. Total height is commonly three to eight centimetres with a head five to eight millimetres wide.

The velvet — the defining character

This is what a hand lens is for. Both the head and the stalk are covered in a fine dark velvety pile: stiff, dark brown to black, thick-walled, pointed bristles called setae that project beyond the surface of the fertile layer. At ten times magnification they show as a bristly halo along the outline of the fruitbody, best seen against a bright sky or a pale card. On the stalk they are usually denser and easier to see; on the head they can be sparse enough that you need to look at the edge in profile.

Run the fruitbody between finger and thumb: it feels minutely rough and dry, not slimy. Both the velvety texture and the absence of any gluten separate this genus at a stroke from most of the smooth earthtongues, which are either dry and polished or distinctly viscid.

Stalk and base

The stalk is the same dull black as the head, one and a half to three millimetres thick, sometimes slightly flexuous, and it descends into the moss layer without a bulb or a rooting cord. Clean the base and you find the stalk running into the soil among moss rhizoids and grass roots, bound with a little soil but with no rhizomorphs, no volva and no attachment to wood. Establishing that a black club is emerging from turf rather than from a buried stick is an early and important elimination step.

Flesh in section

Slice a fruitbody lengthways with a sharp blade. The interior is solid and tough-elastic, blackish to very dark grey-brown throughout, with no white core, no chambering and no gelatinous zone. It is rubbery rather than brittle, and it bends before it breaks. There is no colour change on cutting; the cut face simply looks the same dark tone as the outside. There is no distinctive smell.

Reading the spores

There is no spore print in the mushroom sense here — this is an ascomycete, and the spores are shot from asci over the whole fertile surface rather than dropped from gills. To get a deposit, place the head on a glass slide inside a covered dish overnight, or simply squash a scraping of the fertile layer directly.

What you find under the microscope is spectacular and settles the identification. The ascospores are enormous by mushroom standards: cylindrical to narrowly fusoid, dark brown, roughly eighty to one hundred and fifty micrometres long by five to seven wide, and divided by numerous cross-walls. Mature spores of this species typically show around fifteen septa, though counts range lower in immature material. Between the asci sit the setae — dark, thick-walled, sharply pointed, projecting well beyond the hymenium — and their presence is the genus character for Trichoglossum. If the hymenium has no setae, you are in Geoglossum instead, whatever the field impression suggested.

Habitat, season and ecology

Expect it from late summer to late autumn, peaking in the same weeks as waxcaps and fairy clubs. That is not a coincidence: earthtongues belong to the assemblage of fungi characteristic of old, undisturbed, low-nutrient grassland, alongside Hygrocybe waxcaps, Entoloma pinkgills and coral fungi. Where these appear together, the grassland has usually escaped ploughing and fertiliser for a long time, and surveyors treat the group as an indicator of grassland continuity and conservation value.

The fungus lives in the soil and moss layer, its mycelium threaded through humus and moss litter, and it fruits in damp, mild weather after rain. It also occurs on mossy banks, in dune grassland, on peaty ground and occasionally in mossy woodland clearings, but heavily fertilised or recently disturbed turf almost never supports it.

Separating it from the closest look-alikes

Geoglossum species are the main confusion and share the black tongue outline exactly. The separation is the setae: Geoglossum has none, so its surface is smooth to the lens, either dry and slightly polished or, in some species, distinctly glutinous and shiny. If the outline of the fruitbody is not bristly at ten times magnification, it is not Trichoglossum.

Other Trichoglossum species need microscopy. Trichoglossum walteri has spores with around seven septa rather than fifteen and sparser setae on the stalk; a septum count on mature spores is the working separation.

Microglossum species share the shape but not the colour, being olive, green, yellowish or purple rather than black, and having smooth surfaces.

Xylaria hypoxylon, Candlesnuff, grows on dead wood, is usually branched like antlers, and is white and powdery at the tips.

Xylaria polymorpha is far stouter, club-shaped and knobbly, grows from buried hardwood, and shows a solid white interior when cut — the opposite of the uniformly black flesh here.

Cordyceps species that produce small dark clubs in turf arise from buried insect larvae or from other fungi; excavate the base and the host is visible.

A field routine

Unimproved mossy grassland in autumn; small black tongues in a scattered troop; head flattened and clearly set off from the stalk; hand lens shows a bristly velvet outline on head and stalk; cut face uniformly dark and rubbery, no white core; base in moss and soil, not wood. Confirm with a slide: setae plus very long, many-septate brown spores.